Being products which absorb aqueous solutions, water-absorbing polymers are used to produce diapers, tampons, sanitary napkins, panty liners, wound dressings and other hygiene articles, but also as water-retaining agents in market gardening.
The production of water-absorbing polymer particles is described in the monograph “Modern Superabsorbent Polymer Technology”, F. L. Buchholz and A. T. Graham, Wiley-VCH, 1998, pages 71 to 103.
Water-absorbing foams based on crosslinked monomers comprising acid groups are known, for example from EP 0 858 478 B1, WO 97/31971 A1, WO 99/44648 A1 and WO 00/52087 A1. They are produced, for example, by foaming a polymerizable aqueous mixture which comprises at least 50 mol % of neutralized, ethylenically unsaturated monomers comprising acid groups, crosslinker and at least one surfactant, and then polymerizing the foamed mixture. The polymerizable mixture can be foamed by dispersing fine bubbles of a gas which is inert toward free radicals, or by dissolving such a gas under elevated pressure in the polymerizable mixture and decompressing the mixture. The foams are used, for example, in hygiene articles for acquisition, distribution and storage of body fluids.
It was an object of the present invention to provide a feminine hygiene absorbent article comprising water-absorbing polymer particles with an improved profile of properties, such as a high saline flow conductivity (SFC) and especially a high free swell rate (FSR).